The present invention relates to a process for application of coatings to a substrate to impart a simulated weathered-copper appearance and articles produced thereby. The process may utilize water-reducible and solvent-based "visulescent" (defined below) coatings which result in the perception of color effects dependent on viewing angle or the angle of incident light. In the decorative architectural and building trades, copper metal, usually in the form of sheet copper, has enjoyed a continuing acceptance since ancient times to the present with architects and builders. Both historical landmarks and modern architecture utilize copper panels because of its favorable weight, strength, formability and aesthetic appeal. External copper as a building component is widely used for external purposes in siding, roofing and structural components. More recently, additional applications have been found to supply imaginative, decorative applications for internal purposes. Architects are constantly developing new techniques for using copper, including the concept of laminating copper to other materials, such as plywood and asbestos.
Copper sheet and metal applications are unique in that the fresh metallic copper appearance changes on aging and exposure. Weathered-copper proceeds through multiple changes each affording a different color perception. These various colors of copper enhance the structures on which it is used and provides a distinctive character thereto. Copper, when exposed to the elements, passes through various brown and green shades and ultimately weathers to a blue-green or gray-green color, a process which takes five to fourteen years. The brown shades are called "statuary finishes" and the green shades are called "patinas." Statuary finishes (metal to brown) can be maintained somewhat by application of raw linseed oil. Patina finishes depend on the weathering property of copper and occur over many years of aging. Solutions to treat the copper substrate have been used to accelerate the patina development but have not proven entirely satisfactory. Research programs to develop reliable artificial patinating techniques are ongoing. The instant process relates to a process for imparting the desirable weathered-copper appearance to various substrates which overcomes the undesirable aspects of metallic copper. Such coated substrate can readily be used in place of the metal sheeting and yet provide the aesthetic copper metal and patina appearances which are immediate, relatively permanent and are not dependent on weathering.
Although the prior art teaches coatings containing metal powders, Applicants are aware of no coatings that approach the process of the instant invention or of any metal substrate having the unique characteristics of those shown herein. It is known in the art that coatings pigmented with copper powders can be treated to provide a weathered appearance; these methods depend on the further treatment of such coated panels with acids and other chemicals which attack the copper particles in the coating to oxidize them in a manner akin to the external weathering of sheet copper. Such articles exhibit only the weathered appearance and unlike those of the instant invention are subject to continuing degradation due to atmospheric and oxidative conditions. The instant coating and process has overcome the deficiencies of the prior art materials.